P19319: Lockheed ATLAS II
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Preliminary Detailed Design

Table of Contents

Team Vision for Preliminary Detailed Design Phase

The goal of the Preliminary Detailed Design Phase was to create a detailed design plan for the project proof of concept. By the end of the phase, we completed the following:

Mechanical Design: Feasibility, Prototyping, Analysis, Simulation

Model

We performed extensive research on various 3D printer concept designs to better understand how to most effectively model a Cartesian coordinate linear positioning system. A design that we believe provides the best guide to follow is that of the Prusa i3 Mk3 model. A picture of the system can be found below.

Prusa i3 3D Printer model

Prusa i3 3D Printer model


We want to model the carriages of our system in the same fashion as the Prusa. The picture below shows an example of how the timing belts are hooked up to the carriage.

Prusa i3 3D Printer Timing Belt Carriage

Prusa i3 3D Printer Timing Belt Carriage

Although it provides the basic framework for our design, it will need to be heavily modified to meet our needs, such as adding a scalability aspect, a camera mount, etc. Another important modification is the movement in the vertical axis. The Prusa model utilizes a lead screw for this movement, which is very slow. This isn't an issue for a 3D printer but would be for our design. In order to meet our speed requirements, we needed to decide on a drive system for the vertical Y-axis. Including the lead screw used for the Y-axis and the timing belt used for the X-axis, we researched four different linear positioning systems shown in the table below.

Pugh Chart for Linear Positioning Systems

Pugh Chart for Linear Positioning Systems

With the level of accuracy and speed required for our system, we decided to further explore the ball screw drive and timing belt drive options.


Ball Screw Drive

Background

Ball screw drives essentially consist of a screw and a nut. The screws are manufactured to a high precision grade and the nut is similar to a ball bearing system, where steel balls in the nut roll along the grooves of the screw. The screw is rotated by the motor and the nut travels based on the direction of rotation.
Ball Screw Animation

Ball Screw Animation

Design Parameters & Calculations

The Ball screw system would have Fixed-Floating end supports. This means that one end would be rigid and fixed with double bearings to the motor and motor housing and the other end would be fixed to a single bearing and a supporting block connected to the MFD.
End Fixity Supports

End Fixity Supports

The following is a table of nominal parameters used that will fulfill the engineering requirements of our system:

Ball Screw Parameters

Ball Screw Parameters

The lead is a function of the desired speed of the system and the motor torque. Through the following calculation, the lead of the system would need to be 35.56 mm or larger.

 Ball Screw Lead Calculation

Ball Screw Lead Calculation

The cost of implementing a ball screw drive would be between $500 and $1000 for the full-size range of the ATLAS Too system.

Timing Belt Drive

Background

The timing belt drive system translates rotary motion into linear motion through a pulley. The pulley is directly attached to the motor and through a pulley at the opposite end of the system and to the carriage.
Timing Belt Animation

Timing Belt Animation

Design Parameters & Calculations

Based on the engineering requirements specific to our design, the specifications for the timing belt and pulleys were determined, as shown in the following table. The system will feature T5-pitch trapezoidal belts with widths of 15mm. Each belt will be secured to the component it is moving by being secured around knobs on the back of the component.
Timing Belt Parameters

Timing Belt Parameters

The cost of implementing the timing belt linear drive system would be about $100 across the full-size range of the ATLAS Too system.

Final Decision

We decided to proceed with the Timing Belt linear positioning drive largely due to cost.

Scalability

To simplify the scope of the design, we decided to create two size ranges for the final product. Our initial engineering requirement was to create a device that is compatible with MFDs as small as 6"x9" and as large as 30"x30". The two size ranges of the final product will be: Small to Medium and Medium to Large. The Small to Medium size range will cover MFDs as small as 6"x9" and as large as 14"x19". The Medium to Large size range will cover MFDs as small as 14"x19" and as large as 24"x30".

Hardware Drawings

Isometric View of System Design, without Camera Mount

Isometric View of System Design, without Camera Mount

Top View of System Design, with Camera Mount

Top View of System Design, with Camera Mount

The mechanical drawings for the design can be found here:

Assembly Drawings

Feasibility

Linear Actuator

Due to the tap speed requirement, an analysis was performed for the linear actuator from the previous ATLAS team and the linear actuator that we planned on purchasing.

Linear Actuator Speed Analysis

Linear Actuator Speed Analysis

Power Analysis

Power Analysis Table

Power Analysis Table


From the Power Analysis Table, we need a Power Supply of at least 12V and 10A. We plan to do more research on a power supply next phase.

Additionally, we will be looking into using a second Raspberry Pi in order to break the system into modules.

Electrical Design

Electrical Drawings

High Level System Schematic

High Level System Schematic


Motor Wiring Diagram

Motor Wiring Diagram


Linear Actuator and FSR Wiring Diagram

Linear Actuator and FSR Wiring Diagram

Software Flowchart

The flow chart below represents the top level software design for the atlas and its subcomponents.
Software Flowchart

Software Flowchart

Configuration Management Plan

Configuration Management

Configuration Management

Bill of Materials (BOM)

From the known design components, a Bill of Materials was created for the Proof of Concept.
Bill of Materials

Bill of Materials

The budget created in Phase II was also updated to reflect the purchases made so far.

Updated Budget

Updated Budget

The full Phase III updated budget worksheet can be found here.

Test Summary Matrix

The test summary matrix shows the relationship between the test plans and the risks that are associated with this project. The entire document can be found here.
Test Summary Matrix

Test Summary Matrix

Test Plans

The test plans are a complete document of criteria and procedure for testing critical requirements of the system. The example test plan is shown below. The entire document can be found here.

Test Plans

Test Plans

Risk Assessment

Updated Risk Assessment

Updated Risk Assessment

Risk Tracking Chart

Risk Tracking Chart

You can find the full document for the risk management strategies here.

Phase III Close-Out & Remaining Actions

These are the major tasks that were not reached this phase. Many are due to unexpected delivery delays which set the team back far more than expected.
Phase 3 Closeout Items

Phase 3 Closeout Items

Peer Review Feedback

After the Problem Definition phase, the team participated in a peer review so that each member could learn how they can improve to best help the team. The main point that each member learned from that review and what they did to address it is summarized in the table below. An additional peer review will be done following the Systems Design phase.
Peer Review Table

Peer Review Table

Plans for Next Phase

Plans for the next phase are shown below.
Phase 4 Plans

Phase 4 Plans


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